Recording cathode-ray tube having an electron penetrative window

ABSTRACT

There is disclosed a recording cathode-ray tube having an electron beam penetrative window which permits the electron beams of low energy level to pass it, and which has sufficient physical strength against breakage because of a unique supporting or reinforcing means applied to the electron penetrative membrane. Such device has several other advantages which are also disclosed. There are also disclosed combinations of such device and a magnetic field, which present improved resolution to the record.

United States Patent Inventors Yoshihiro Uno Machida-shi; I-laruo Maeda, Tokyo; Yujiro Koike, Tokyo, all of Japan Appl. No. 882,394

Filed Dec. 16, 1969 Patented Oct. 5, 1971 Assignee Matsushlta Electric Industrial Co. Ltd. Kadoma-shi, Osaka, Japan Priority Oct. 3, 1966 Japan 41/65873 Continuation of application Ser. No. 671,039, Sept. 27, 1967, now abandoned.

RECORDING CATHODE-RAY TUBE HAVING AN ELECTRON PENETRATIVE WINDO} Primary Examiner- Rodney D. Bennett, J r. Assistant Examiner-J. M. Potenza Attorney-Stevens, Davis, Miller & Mosher ABSTRACT: There is disclosed a recording cathode-ray tube having an electron beam penetrative window which permits the electron beams of low energy level to pass it, and which has sufficient physical strength against breakage because of a unique supporting or reinforcing means applied to the electron penetrative membrane. Such device has several other advantages which are also disclosed. There are also disclosed combinations of such device and a magnetic field, which present improved resolution to the record.

5 Claims, 15 Drawing Figs.

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SHEET t [If 4 INVENI" OR 5 vonmmw u-vO "HRH-0 new yu Jinn prance ATTORNEYS RECORDING CATHODE-RAY TUBE HAVING AN MQNI W This is a continuation of application Ser. No. 671,039, filed Sept. 27, i967, and now abandoned.

This invention relates to a recording cathode-ray tube, particularly to a recording cathode-ray tube having means penetrative by electron beams: in other words, a kind of window through which the electron beams of relatively low energy level generated within a vacuum enclosure can be transmitted out to the surrounding atmosphere with little dispersion of scattering.

Generally, electron beams impart various physical and chemical efl'ects upon the substances exposed thereto depending on the electric charge and energy level of the electrons. This property of electron beams find many applications in various fields including medical equipment, electronic instruments and electronic recording devices.

The electron beams can be used also as electronical writing means or recording means in a recording cathode-ray tube, some existing examples of such tube being the electrostatic printing (or recording) tubes and so-called optical fiber tubes. As the electron beams are easily and quickly controllable as to the size, position, density, energy and other parameters thereof, the printing or recording by electron beams provides many advantages over the conventional printing methods, permitting a rapid operation, remote controlling (for example, facsimile) and combination with an electronic computer. This invention relates to another and improved printing tube having the above-mentioned features, in which the electron beams projected from an electron gun within the tube are transmitted to the outside atmosphere (normally, the air) through a membrane, to act on the recording paper.

Comparing to the conventional printing tubes in which the electron beams act on the recording paper after being transformed into light beams or in the form of electric charge, the membrane type printing tube according to this invention provides more varieties of the recording modes and higher sensitivity of the recording, as the excellent features inherent to the electron beams can be fully exploited in the cathode-ray tube of this invention.

However, the electron beams undergo a dispersion as to the energy and direction thereof when the beams penetrate the membrane. Further, the membrane which is made of a very thin material is susceptible to breakage. This invention provides a printing tube of electron beam penetrative type which is devoid of the above-mentioned disadvantages.

The windows for transmitting the electron beams are generally made in the form of an oblong slit. According to this invention, this window is reinforced by a supporting plane having one or a number of holes or mesh, or a grid. Such supporting plane serves also to keep the recording paper from directly contacting the membrane, to improve the resolution, and to converge the scattered beams by facilitating application of a magnetic field coaxially with the direction of projected electron beams or by allowing provision of an array of small magnetic lenses adjacent to the membrane, resulting in an improved resolution if the recording paper is spaced from the membrane.

Generally, electron beams of high energy level over 50 Kev. are used in the medical equipment such as Liniac, the non destructive testing devices and the like, in which the electrons projected from an electron gun are accelerated in a vacuum enclosure of about mm. Hg or higher and are transmitted out to the atmospheric environment through a window of an aluminum membrane. In such case, comparatively little scattering of electrons occurs when the electron beams pass through the membrane because of a sufficiently high energy level of the beams, and therefore a sufiiciently thick membrane can be used to provide an assured strength. Moreover, for some applications, a little scattering might not be an important problem.

Electron beams of comparatively low energy level below 50 Kev., are susceptible to scattering when the beams are transmittedthrough, for example, an aluminum membrane, thus presenting a great disadvantage to the application of the beams for recording or similar uses. Such electron beams of low energy level are now used in the oscilloscopes, television receivers and other measuring and displaying devices. In such devices, the energy of the electron beams is transformed into light energy by the fluorescent material before being displayed on the screen. Such display is inherently accompanied by poor resolution owing to the halation and dispersion by the glass. Further, if the recording is to be made by photograph, the available light is reduced during a period when it is transmitted through the glass panel. As one solution to the abovementioned problems, a new type of cathode-ray tube has been introduced in which a bundle of glass fibers, such as the socalled fiber optics, is used in the plane separating the vacuum inside from the atmosphere. However, this device is not different from the above-mentioned tubes in the fact that the electron beams are transformed into light. One device in which the electron beams are taken out without being converted into light, is the so-called pin tube (or electrostatic printing tube). In this tube, the electron is taken out through a bundle of metal pins penetrating the separating plane. By this means, however, only the electric charges carried by the electrons can be taken out but the energy can not. Moreover, the static capacitance between pins impairs the resolution. That is, there has been found no device that enables the electron beams of low energy level to be taken out from a vacuum enclosure without substantial scattering.

As an electron has a high e/m (electric charge to mass ratio), actually the highest of all existing particles, the electron beams can be easily controlled as to the energy, position and size thereof. Even an electronic spot of less than 10 micron in diameter can be easily obtained. When the electron beams are caused to act directly on a displaying medium or a recording medium, a highly effective operation is attainable by the excellent resolution and by the separate or combined use of the electric charge and energy thereof. Generation and control of the electron beams are possible only in vacuum of about 10" mm. Hg or higher. Accordingly, the displaying or recording medium must be included within the vacuum enclosure with the electron gun. This causes contamination of the vacuum and moreover necessitates a more powerful evacuating system and a longer evacuating hours. Therefore, it will be seen that it is very advantageous if the electron beams can easily pass the partition which separates the vacuum space containing the electron gun from the atmosphere where the displaying or recording medium is placed. In the conventional cathode-ray tubes, such partitions as mentioned above are made of aluminum or other metallic membrane or of a film of mica. However, the electron beams cannot pass entirely freely through such membrane or film. Elastic or nonelastic collision of the electrons against the lattice of the substance constructing the membrane will reduce the energy of the electron and cause dispersion of the energy and direction. The degree of such dispersion is a function of thickness of the membrane, and the incident energy of the electron beam, depending on the material of membrane. When the electron beams are to be used for display or recording, the scattering of the beams after passing the membrane will impart a definite bad effect on the resolution.

According to this invention, a cathode-ray tube for displaying or recording an information with high resolution is provided by separating two different environments, for instance, high vacuum space and the atmosphere or low vacuum space, with a membrane partition reinforced with supporting plane having small holes or mesh, the electron beam generator being placed in the high vacuum side, the recording or displaying medium being placed in the atmospheric or low vacuum side, and the electron beams being taken out through said membrane partition, thus eliminating the necessity of placing the displaying or recording medium in the high vacuum environment.

Now, this invention will be described in more detail, in the example of the embodiments and with reference to the accompanying drawings in which:

FIG. I is a diagram showing the distribution of scattering electron beams in the relation to the scattering angle after the beams have passed a metallic membrane,

FIG. 2a is a sectional view of a part of the electron beam penetrative means used in an embodiment of this invention,

FIG. 2b is a diagram illustrating the function of the means shown in FIG. 24,

FIG. 3a is an enlarged sectional view of another embodiment of this invention,

FIG. 3b is a diagram illustrating the function of the means shown in FIG. 3a,

FIGS. 4, 5a, 5b, 6a, and 6b are sectional views of other embodiments of this invention,

FIGS. 7 to 9 and FIGS. 10 and II are diagrams illustrating still other embodiments of this invention.

Referring to FIG. 1, the diagram shows the scattering of 20 kev. electron beams when the beams pass an aluminum membrane 3,000 A. thick. It will be seen from the diagram that if the recording medium is placed in contact with the surface of membrane, the scattering of the beams will scarcely exceed the extent equivalent to the thickness of the membrane. However, it is not practical to place the recording medium in contact with the membrane, because of lack of flatness of the surface and the fragility of the membrane.

According to this invention, the electron beam penetrative membrane is reinforced and at the same time, the scattering of the beam is reduced, thus providing an improved resolution. One embodiment of such means is shown in FIG. 2. The anticipated maximum pressure difference between two places separated with the membrane is one atmospheric pressure. In FIG. 2a, the reference numeral 2 indicates one of a number of small holes which are arranged along a line or over a plane on a metallic or nonmetallic plate, 3 indicating the wall of the hole. Numeral 4 is the recording medium, including a photograph film of silver halide type, polymeric materials, various dyestuffs, electrostatic printing materials and the other materials sensitive to electron beams. Numeral 5 is the supporting member for the recording medium 4. If the recording medium 4 is moved two-dimensionally, only one hole may be sufficient for the purpose. This structure should have enough strength to withstand the anticipated static and dynamic pressures. The resolution of recording depends upon the pitch (or distance between centers) of the holes (or the diameter of the hole when only one hole is provided), assuming that the resolution of the recording medium is sufficiently high. It is preferable that the walls of holes are as thin as possible. The membrane of the partition indicated by numeral 1 is made of aluminum or other metallic material, mica, polymeric materials and other suitable materials. Taking an aluminum membrane as the example, the required thickness of the membrane under one atmospheric pressure is determined roughly by the following formula.

rgrxw cm. (l) n where 1: thickness of the membrane in cm.

r: radius of the hole in cm.

If the diameter of the hole (2r) is assumed to be 10 micron, the thickness of the membrane is required to be more than 1000 A. From the standpoint of the dispersion of the electron beams as to the energy and direction as well as the loss of energy, the thinner membrane will be better, the value of t determined from the above formula (1) being the best. However, when a supporting structure having small holes or mesh, or a structure of lattice is used to reinforce the membrane as in this embodiment, the supporting structure per se controls the dispersion of the beams, portions of the beams that have passed the membrane at a low energy level and big dispersion angle will collide against the walls of the holes, mesh or lattice and will be extinguished or caused to generate secondary electrons of low energy level (mostly lower than ev.) which, in turn, collide against the walls of the holes, mesh or lattice, as they are generated in random directions, and are extinguished eventually. Accordingly, the electron beams that have undergone comparatively little dispersion in the energy level and direction are transmitted through the holes. Since the resolution depends solely upon the formation of the hole. mesh or lattice as previously described, the membrane can be made sufficiently thick to assure the safe operation, only if the energy loss caused in the course of penetration is tolerably small for the purpose of usage. The average energy levels of the electron beams before and after passing the membrane are indicated approximately by the following formula (2) E in Eout q: Kt (2) where E in: Energy of electron incident to the membrane in ev.

E out: Energy of electron leaving the membrane in ev.

t: Thickness of the membrane in cm.

K: A constant 1X10 for Al) K=Zp/ Aa where 2: Atomic number p: Density A: Atomic weight a: A constant Assuming that the membrane of AI is used, and E in is 20 kev. and t is 1000 A., the energy E out is determined to be 19.993 kev., accordingly the average energy loss being approximately 5 ev. If it is assumed that t is l0 l,000 A., the other parameters being the same, then the average energy loss will be approximately 50 ev., a very small value compared with the incident energy.

When the displaying and recording medium 4 is placed in contact with the supporting structure having the holes, mesh or lattice as shown in FIG. 2a, the display or record on the medium 4 will be striped or latticed depending on the formation of the hole, mesh or lattice, as shown in FIG. 2b. These stripes or lattice, however, can be extinguished by placing the medium 4 in a spaced relation to the supporting structure as indicated in FIG. 3a, and by causing the penumbras from two holes to overlap as shown in FIG. 3b. The optimum length of the gap differs depending on the formation of the holes, mesh or lattice. The desirable gap length for round holes is given by the following formula (3 approximately.

d=l (Rr)/r (3) where d: Desired gap length 1: Depth of holes R: Half of the center distance of two adjacent holes r. Radius of hole A larger gap will give a poorer resolution, while a smaller gap will produce a striped image. If the value of R is sufficiently small, the stripe will not be recognizable, though it will impair the best contrast when the saturated region of the characteristics of the displaying or recording medium is involved in the operation. It should be noted that this gap serves also to protect the surface of the membrane from being scratched and to prevent the minute particles produced by scratching to enter into the holes.

FIGS. 4 to 6 schematically show the cathode ray tubes or portions thereof in which are used the means to deliver the electron beams which have undergone angular dispersion in a direction of electron motion in the manner of nonelastic scattering that is caused on impact of the delivered electrons with the molecules of the thin membrane while the electrons pass through thin membrane to the recording medium without scattering. In FIG. 4, numeral 6 is the front plate made of a material of high magnetic permeability, 7 is the membrane of, for example, aluminum attached to cover a group of holes or slits 8 provided in the front plate 6, laterally along one line or a plurality of lines. The membrane 7 seals the cathode-ray tube 9. The electron beam 11 projected from the electron gun l0 and reflected through a deflecting system (not shown) are transmitted through themembrane 7 and are taken out of the tube. FIGS. 5a and 511 show an enlarged and detailed view of the front plate 6 and the electron permeable membrane 7 of the cathode-ray tube shown in FIG. 4. FIG. 5a shows a cross section of the front plate 6 showing a plurality of holes 8. The

electron permeable membrane 7 is vacuum-tightly attached to the surface of the front plate 6. FIG. 5b also shows a side cross section of the front plate indicating a slot 8 provided in the front plate 6. FIG. 6 shows a device for obtaining a record directly from the cathode-ray tube 9, specifically FIG. 6a shows a sectional view of the tube with a plurality of holes 8 arrayed in the front plate 6 and FIG. 6b shows a side sectional view of the tube with a slot 8 provided in the front plate 6. The recording medium 14 is positioned opposite the plurality of holes or slot 8 in the front plate 6, numeral 12 indicates a magnetic pole piece made of a material of high permeability, arranged in opposed position to the front plate 6, the recording medium 14 being interposed between said pole piece 12 and the front plate 6, and numeral 13 indicates a magnet or magnets arranged so that two poles thereof are in contact with the front plate 6 and the pole piece 12, thus a magnetic field parallel to the electron beams is provided between the front plate 6 and the pole piece 12. The electron beams which are transmitted through the small holes 8 and the membrane 7, undergo dispersion by the collision with the atoms constituting the membrane 7, and start to scatter in the direction of the dispersion upon emerging out of the membrane 7. However, the scattering beams are converged by the magnetic field between the front plate 6 and the pole piece 12, and are delivered to the recording medium 1 4 without scattering, thus resulting in a recording of high resolution.

FIGS. 7 to 9 show schematically another cathode-ray tube and the operation thereof, in which are used means to deliver the electron beams scattered by the membrane to the recording medium without scattering. In FIG. 7, numeral 15 indicates an electron gun, which is contained in a glass enclosure 18 of high vacuum along with the deflecting plates 16. The metallic membrane 19 of, for example, aluminum covers the hole 19' in the front plate 18 and constitutes the window through which the electron beams are transmitted. The magnetic assembly 20 consisting of two magnetic plates 20' and 20" interspaced and supported by anonmagnetic spacer 21, is provided with a hole of substantially the same size as said hole 19' and in aligned relation to said hole 19'. The exciting coil 23 is provided on the core 23' to produce a magnetic field between two magnetic plates 20' and 20", the coil 23 being supplied with DC current from the source 24. The recording medium 22 is placed in opposed position to the hole 19', and the intended information is recorded on the medium 22 by the electron beams which are transmitted through the membrane 19 covering the aperture 19'. If a permanent magnet is used for the magnetic plates 20' and 20", the exciting coil 23 and the source 24 will be spared. The electron beams 17 projected from the electron gun 15 are deflected" through the deflector 16 and scanned over the holes. The beams that pass the membrane undergo dispersion and start to scatter upon emerging out of the membrane 19. However, the scattering beams are converged through the magnetic lens formed by the magnetic plates 20' and 20" adjacent to the membrane 19, as seen from FIG. 9. If the device is adjusted so that the image of the electron beams is focused on the recording medium, the image will not be affected by the dispersing effect of the membrane, thus presenting an image of high resolution. In the above embodiment, the membrane 19 is positioned outside of the magnetic field provided by the magnetic plates. However, it will be understood that the membrane can be positioned within the magnetic field, being supported by the magnetic plate.

Now, another embodiment of this invention will be described hereinafter, with reference to FIGS 10 and I I.

The electron gun 3| and thc deflecting plates 32 are contained in u high vacuum enclosed by the glass enclosure 34. The membrane 35 covering the hole 35' provided in the front plate 34 is made of a metallic material such as aluminum or nickel, or a nonmetallic material such as mica, and constitutes the electron beam penetrative window. On one arm 36f of the C-shaped (in the section) magnetic structure 36, a hole 41 substantially the same in diameter as the hole 35 is provided in the aligned relation to the hole 35. The other and opposite arm 36" of the C-shaped structure 36 is provided with a protruded portion 36" in the opposed relation to the hole 41, to concentrate the magnetic flux to this portion. On the top of the protruded portion 36", the recording medium 40 is placed facing to the holes 35 and 41. The gap between the recording medium 40 and the fiat part of arm 36' is filled with the spacer 39 of nonmagnetic material. The exciting coil 37 wound on the structure 36 and energized by DC current from the source 38, produces a uniform magnetic field between the arms 36' and 36". The broken lines in FIG. 11 represent the magnetic lines of force. It will be seehthat the recording medium is positioned in the uniform magnetic field by the magnetic structure 36. The curved solid lines in FIG. 11 indicate the loci of electron beams. The electron beams projected in the normal direction to the penetrative window, collide with the atoms constructing the membrane, undergo the dispersing effect, and start to scatter when leaving the membrane. However, the magnetic lens adjacent to the membrane and the ensuing uniform field of high intensity, gives the beams a circulating movement. Thus, the electron beams proceed with a combined motion of convergence and rotation. (The rotating components in the movement of the beams are not shown in FIG. 11). The lens function of the magnetic field is determined by the arrangement of the magnet 36 having the hole 41, the intensity of the magnetic field and the energy level of the electron beams. The largest radius of said rotating movement of the beams is determined by the intensity of the magnetic field and the energy level of the electron beams.

If the lens action of the magnetic field is neglected as an extreme example, the radius of said rotating movement of the beams is determined by the following formula.

V Voltage required to accelerate an electron up to the velocity equivalent to that of the electron just emerging from the membrane v 9: Angle determined by the normal line of the membrane and the direction of motion of the electron just leaving the membrane [3: Intensity of the magnetic field (W /m.)

The maximum ,deviation of the beam from the incident direction is thus determined as 2r calculated by the above formula. It is assumedthat V is 20 kv., 0 is 10 and B is'l, then the approximate value ofr will be 0.2 mm. (2 Xl0 m.). Since such rotating or spiral motion brings the electron back to the original course after every one round, the above-mentioned deviation can be minimized by properly selecting the position of the recording medium. It will be understood that the shape of the holes 35 and 41' need not to be necessarily round. Each may be rectangular hole or even a slit. In either case, the scattering of the beams caused in the course of passing the membrane can be limited by the converging and rotating effect in the vicinity of the hole or slit and bythespiral proceeding in the ensuing uniform magnetic field. Again, the membrane may be positioned either inside or outside of the magnetic field.

As described hereinbefore, according to this invention, the electron beams, if once scattered by the membrane, are delivered to the recording medium with no significant scattering, an accordingly with a high resolution, because the beams are continuously acted on by the magnetic field which extends between the membrane and the recording medium substantially in parallel to the intended direction of the beam, thus converging the beams emerging from the membrane. It should be noted that the scattering of the beams by the atmosphere is negligibly small as compared with that by the membrane.

According to this invention, as described above, the electron penetrative membrane is reinforced by a supporting plane having holes or mesh or a lattice, and at the same time, impairment of the resolution owing to the scattering of the beam can be prevented by the use of the shadow made by the supporting structure.

Further, according to this invention are provided a cathoderay tube for direct recording, in which the front plate is made of a magnetic material of high permeability, a magnetic field being provided between said front plate and a pole piece provided in opposed relation to said front plate, and in which the electron beams passing an array of small holes or slits are converged by said magnetic field to be taken out without significant scattering, thus allowing a recording of high resolution.

Further, the same object can be attained by providing a magnetic lens for converging the electron beam which are transmitted through an electron penetrative aperture of membrane.

We claim:

1. A recording cathode-ray tube for recording information on a recording medium comprising an evacuated glass envelope having a front plate with at least one orifice therein, an electron gun mounted in said envelope and directed at said orifice, an electron beam penetrative means covering said ori fice and comprising a membrane through which electron beams are transmitted sealingly closing said orifice to separate the vacuum from atmosphere and supporting structure means having a plurality of small holes at least in the portion spanning said orifice, said recording medium being spaced from said supporting structure by a gap no greater than the length d determined by the formula d=21(R-r)/ r where l is the depth of the holes;

R is half of the center distance of adjacent said holes in said supporting structure means; and

r is the radius of said holes in said supporting structure means.

2. A recording cathode-ray tube according to claim 1 in which said supporting structure means is selected from the group consisting of holed plates, mesh, lattice, and slotted plates, said membrane being mounted on the vacuum side of said supporting structure.

3. A recording cathode-ray tube according to claim 1 further comprising magnetic field means including magnetic lens means for converging electron beams emerging from said electron beam penetrative means.

4. A recording cathode-ray tube according to claim 1 further comprising means fonning a substantially parallel magnetic field to converge the electron beams emerging from said electron beam penetrative means, said recording medium being placed in said magnetic field.

5. A recording cathode-ray tube according to claim 1 in which said membrane is mounted on the atmospheric side of said supporting structure, magnetic field means adjacent said membrane and adapted to cause said electron beams to converge as they pass through said membrane into the atmosphere.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 1, 005 Dated October 5, 1971 Inventor) Yoshihiro UNO Haruo MAEDA Yuj iro KOIKE It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

The claim for Convention Priority was incomplete due to errors in this patent and should also include the following:

Japan, Patent Application No. 72658/66 filed November 2, 1966 and Japan, Patent Application No. 7-2659/66 filed November 2, 1966.

Signed and sealed this 27th day of June 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attasting Officer Commissioner of Patents USCOMM'DC 603764 09 

1. A recording cathode-ray tube for recording information on a recording medium comprising an evacuated glass envelope having a front plate with at least one orifice therein, an electron gun mounted in said envelope and directed at said orifice, an electron beam penetrative means covering said orifice and comprising a membrane through which electron beams are tranSmitted sealingly closing said orifice to separate the vacuum from atmosphere and supporting structure means having a plurality of small holes at least in the portion spanning said orifice, said recording medium being spaced from said supporting structure by a gap no greater than the length d determined by the formula d 21(R-r)/ r where l is the depth of the holes; R is half of the center distance of adjacent said holes in said supporting structure means; and r is the radius of said holes in said supporting structure means.
 2. A recording cathode-ray tube according to claim 1 in which said supporting structure means is selected from the group consisting of holed plates, mesh, lattice, and slotted plates, said membrane being mounted on the vacuum side of said supporting structure.
 3. A recording cathode-ray tube according to claim 1 further comprising magnetic field means including magnetic lens means for converging electron beams emerging from said electron beam penetrative means.
 4. A recording cathode-ray tube according to claim 1 further comprising means forming a substantially parallel magnetic field to converge the electron beams emerging from said electron beam penetrative means, said recording medium being placed in said magnetic field.
 5. A recording cathode-ray tube according to claim 1 in which said membrane is mounted on the atmospheric side of said supporting structure, magnetic field means adjacent said membrane and adapted to cause said electron beams to converge as they pass through said membrane into the atmosphere. 